The author of the novel, Mario Puzo, had written the book for money after his well-reviewed works, such as "The Fortunate Pilgrim," flopped. The studio, Paramount, optioned Puzo's treatment hoping for a quickie gangster film; when the book became a huge best-seller, it almost dropped the project, worried about expectations.

The director, Francis Ford Coppola, took the job after several more noted directors (including Elia Kazan, Arthur Penn and Costa-Gavras, according to then-Paramount executive Robert Evans) turned it down. The studio didn't want him -- he'd directed just three major films, none of them hits -- and Coppola didn't want to do it either, but he needed the money to finance his failing countercultural studio, Zoetrope.

It was not the greatest atmosphere to make a movie. At one point, Coppola was almost fired. Tempers were short. Arguments were constant.

"I was pulverized by the story and the effect the film had on me," Steven Spielberg says in documentary material accompanying the new, digitally cleaned and remastered "The Godfather: The Coppola Restoration." The new DVD edition of the "Godfather" trilogy is out Tuesday.

"I also felt that I should quit, that there was no reason I should continue directing because I would never achieve that level of confidence or the ability to tell a story [as well as Coppola did in 'The Godfather']," he added. "In a way, it shattered my confidence."

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" 'The Godfather' hit a cultural nerve," Peter Biskind writes in his history of '70s cinema, "Easy Riders, Raging Bulls." "It was all things to all people, which is perhaps, as marketers would soon realize, a sine qua non for blockbusters."

All this for what was supposed to be little more than a gangster film. But Coppola, as he says in the documentary, saw the source material as more than a B-movie; it was a family saga.

"The Godfather," as the world knows by now, is the story of the Corleone organized crime family: father Vito, sons Sonny (the hothead), Fredo (the slow-witted one) and Michael (the inheritor); as well as their adviser, Tom Hagen, and generations of cops, performers, criminals, politicians, hitmen and hangers-on. The opening words of the first film are "I believe in America," and the sprawling trilogy attempts to show the family's -- and country's -- often violent journey amid the changes of the century.

Coppola and Paramount started battling immediately, Biskind writes. The director wanted to cast Marlon Brando as Vito Corleone, but Brando in 1970-71, when production started, was box office poison.

Coppola also wanted to cast Al Pacino as Michael Corleone, the film's linchpin role. Pacino, who had dazzled on the New York stage, had starred in just one film, "The Panic in Needle Park." Moreover, in the book Michael is tall and blond; the studio wanted someone in that mold, perhaps Robert Redford.

Other actors also came to "The Godfather" with little breakout experience. James Caan and Robert Duvall were veterans -- both had been in Coppola's "The Rain People" (1969) -- but generally in supporting roles. (Caan's breakthrough role, as Brian Piccolo in "Brian's Song," appeared as "The Godfather" was in post-production.)

Then there were those -- the largely ethnic performers who peopled lesser roles -- who weren't known at all. Abe Vigoda, a character actor who had an established career on the New York stage, remembers being called to Coppola's office.

"He interviewed me -- it seems he'd seen me in a play or plays," Vigoda, later to play detective Phil Fish on "Barney Miller," told CNN.com in a phone interview. "One of the [reasons] I think Francis Ford Coppola was interested in me was that nobody knew my face." After some months, Vigoda was cast as Tessio, one of the Corleone capos, or lieutenants. Sidebar: Yes, Abe Vigoda is very much alive

For Vigoda and much of the cast, "The Godfather" was simply "a low-budget movie," in Vigoda's words. But the actor says there was a sense of something bigger at work.

"What we did know was that this was a very creative project," he says. "The actors, director ... I thought, 'This is like doing a play.' It was a very creative job, and strange as it may seem, an easy job for me ... [once I was on the set, I felt] I am Tessio."

Behind the scenes, things weren't going as well. Besides casting, Coppola and studio executives battled over music (the studio didn't like Nino Rota's score) cinematography (Gordon Willis' compositions were considered too dark), locations (Coppola wanted New York; the studio suggested cheaper St. Louis) and even era (Coppola wanted a period piece, the studio wanted the present day).

"There were people on the crew trying to take over the production," Coppola protégé George Lucas recalls in the documentary material.

Oscar-winning sound editor Walter Murch, a longtime Coppola friend, recalls the director being saved by the Italian restaurant scene in which Michael kills two opponents. "The feeling up to that time was, 'What is this movie? It's not turning out the way we thought it would' -- whatever that was," he says in the DVD.

The bickering continued practically up to the release date, with Coppola overshooting the two-hour, 10-minute running time the studio desired and the studio -- though pleased with the final two-hour, 55-minute cut -- uncertain how to please exhibitors who longed for more showings. Paramount came up with two solutions: eliminate an intermission -- de rigueur for long movies -- and open it in many theaters at once.

What emerged was a phenomenon.

"The Godfather" opened wider than any film before, changing Hollywood economics, and became the most successful film in history up to its time. ("Jaws," its successor as box office king, would codify the wide opening once and for all.) The film won best picture, gave the language such lines as "I'll make him an offer he can't refuse," and spawned two sequels, a video game, more Puzo underworld novels and -- essentially -- every gangster work to follow.

"When we started 'The Sopranos,' [referencing 'The Godfather'] was one of the original conceits," says "Sopranos" creator David Chase in the DVD set. Indeed, "Sopranos" characters are forever quoting from the films, thinking of them as a model for the mob experience.

"The Godfather Part II," which came out in 1974, also won best picture -- the only time an original film and its sequel have pulled off the double. With its more intricate structure, many critics consider it the best film of the three. The third film, "The Godfather Part III" (1990), though the least successful, still contains some fine work; as a character on "The Sopranos" said, "A lot of people didn't like it, but I think it was just misunderstood."

The American Film Institute ranks the first film as the second-best of all time, after "Citizen Kane"; Internet Movie Database denizens have ranked it as No. 1 or No. 2 for years. It's been more than 35 years now, and the films still have a hold on the American psyche.

Just ask Joe Mantegna, who starred in "Godfather III" and plays Fat Tony on "The Simpsons" -- a character that owes an obvious debt to "The Godfather."

" 'The Godfather' was the Italian 'Star Wars,' " he says in the DVD.

Or, as Abe Vigoda puts it, "This was true to life. This story, these characters you see in 'The Godfather,' are real. ... It did something to you. It made you part of the real thing."